Conventionally, an ultrasonic diagnostic apparatus can scan the interior of an object with ultrasonic waves and visualize the internal state of the object based on the reception signal generated from reflected waves from inside the object. More specifically, the ultrasonic diagnostic apparatus transmits ultrasonic waves into the object via the ultrasonic probe. The ultrasonic diagnostic apparatus generates a reception signal by receiving, via the ultrasonic probe, reflected waves from inside the object which are generated by acoustic impedance mismatching inside the object. The ultrasonic diagnostic apparatus visualizes the internal state of the object based on the reception signal.
Conventionally, as shown in FIGS. 11 and 12, an ultrasonic probe includes a plurality of transducers which are arranged in an array form and generate ultrasonic waves, a plurality of acoustic matching layers which alleviate the acoustic impedance mismatching between the transducers and an object from the transducers to the object contact surface side, and an acoustic lens which focus ultrasonic waves. The ultrasonic probe also includes an FPC (Flexible Printed Circuit) for signal extraction and a backing material, which are provided on the transducer rear surface side. Each of the plurality of transducers vibrates to generate ultrasonic waves based on a transmission signal from the ultrasonic diagnostic apparatus.
The temperature of a portion of the ultrasonic probe which comes into contact with an object (to be referred to as an object contact portion hereinafter) generally rises as each transducer is driven. In general, proper driving conditions are set for the ultrasonic diagnostic apparatus. If, however, the apparatus keeps generating heat in an unexpected way due to some kind of abnormality, a burn injury or the like may be inflicted on the object.
Under the circumstances, several techniques have been proposed from the viewpoint of an improvement in product safety as follows. As shown in FIG. 13, there has been provided a technique of detecting the temperature of an object contact portion at the time of driving of ultrasonic waves by disposing a temperature sensor such as a thermistor in the ultrasonic probe. At this time, a temperature sensor such as a thermistor influences the propagation of ultrasonic waves, and hence is disposed in a backing material. In this case, the ultrasonic diagnostic apparatus can detect abnormal heat generation and stop driving the transducers by monitoring the temperature of the backing material using the signals output from the thermistor.
It is however necessary to extract a signal line for the thermistor from inside the ultrasonic probe separately from an ultrasonic signal line. The extraction of a signal line of the thermistor complicates the manufacture of an ultrasonic probe, and hence increases the manufacturing cost. In addition, the temperature monitored by signals from the thermistor is the temperature of the backing material but is not the temperature of the object contact portion. That is, the above technique does not directly monitor the temperature of the object contact portion in terms of temporal and spatial detection accuracy, and is an indirect temperature monitoring system.
There has also been proposed a technique of identifying the unused state of an ultrasonic probe by disposing a pressure sensor outside the ultrasonic probe. The main purpose of this technique is to prevent a deterioration in the quality of a product by stopping driving the ultrasonic probe during an unused period. The technique can also contribute to an improvement in product safety by reducing unnecessary heat generation.
It is however necessary to extract a signal line of the pressure sensor separately from an ultrasonic signal line. This poses the same problem as that in the prior art. In addition, this technique cannot cope with heat generation abnormality caused during the use of the ultrasonic probe.